In some instances, it is necessary to know a rotation parameter of an insert bearing, e.g. to determine the speed of a belt conveyer. EP-A-0 908 729 discloses a bushed bearing where a sensor target is fixed to an inner ring and rotates in front of a sensor which is held close to this target and mounted on a sealing device fixed on the outer ring of the bearing. Several relatively complex parts must be mounted within the bushing with high precision. This increases the complexity and the cost of the bearing. Moreover, since the sensor is indirectly mounted on the outer ring, it is relatively difficult to feed with electrical current and some electrical cables must extend from a fixed part of the bushing to the outer ring, with a risk that these cables be damaged.